The present invention relates to ion beam sputter deposition, particularly to the reduction of defects in ion beam sputtered coatings, and more particularly to a method and apparatus for the interception and trapping of particulate matter generated in ion beam sputter deposition for producing low defect coatings.
Defect free films and coatings are desired for many applications, particularly in the field of optics. Substantial effort has been directed to preventing the formation of defects and to the removal of defects resulting from a deposition process. For example, multilayer (ML) coatings for extreme ultraviolet lithography (EUVL) reflective masks must be defect free. Currently, there is no viable mechanism for repairing ML coating defects. Consequently, development of low defect coating technology is a critical problem for EUVL. To date, the lowest defect density of EUVL ML films are fabricated using an ion beam sputter deposition (IBSD) process that utilizes a radio frequency (RF) ion beam source or gun and extraction optics to sequentially sputter Mo and Si targets, for example, with a neutralized argon (Ar+) ion beam. Unwanted particulate material within the IBSD system can acquire an electrical charge due to a combination of electron attachment and ion bombardment as it is transported through the IBSD system. Thus, there has been a need for removing the charged particles before they deposit on a substrate being coated, thereby reducing defects in the deposited material.
The present invention provides a solution to this charged particle problem by providing an electrostatic trap for such charged particles. The invention involves a method and apparatus for the interception and trapping of charged particulate matter generated in ion beam sputter deposition. The interception and trapping of the charged particles is achieved by generating an electrostatic field, by an array of electrodes (1 through n) in the vicinity of the substrate on which a coating is being deposited, and configuring the fields to force the particulate material away from the substrate, thereby producing low density defect coatings.
It is an object of the present invention to produce low defect ion beam sputtered coatings.
A further object of the invention is to provide a method and apparatus for preventing undesired particulate matter generated during ion beam sputter deposition from reaching the substrate being coated.
A further object of the invention is to provide an electrostatic particle trap for use in ion beam sputter deposition systems.
Another object of the invention is to provide an electrostatic particle trap for charged particles generated during ion beam sputter deposition.
Another object of the present invention is to provide a method for the interception and trapping of charged particles by generating electrostatic fields in the vicinity of a substrate being coated, and configuring the fields to force the charged particles away from the substrate.
Another object of the invention is to provide an electrostatic particle trap for charged particles composed of an array of electrodes (1 through n) positioned near a substrate being coated.
Other objects and advantages of the present invention will become apparent from the following description and accompanying drawing. The invention is an electrostatic particle trap for use in ion beam sputter deposition, which enables the fabrication of extremely low defect density films or coatings. The invention involves a method and apparatus for interception and trapping of particulate matter generated in ion beam sputter deposition. The invention involves positioning an electrostatic trap composed of an array of electrodes (1 through n) adjacent a substrate to be coated, generating an electrostatic field in the vicinity of the substrate, and configuring the fields to force the undesired particulate material away from the substrate. The invention enables the production of low defect ion beam sputter deposited multilayers, such as Mo/Si multilayer coatings, for extreme ultraviolet lithography masks, or for other applications requiring low defect density films or coatings.